Fin semiconductor device and method of manufacture with source/drain regions having opposite conductivities

ABSTRACT

A semiconductor device and method of manufacturing a semiconductor device using a semiconductor fin is provided. In an embodiment the fin is formed from a substrate, a middle section of the fin is covered, and then portions of the fin on either side of the middle section are removed. A series of implants is then performed and a gate dielectric and a gate electrode are formed to form a tunneling field effect transistor from the fin.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a divisional of U.S. patent application Ser. No.14/755,156, entitled “FIN SEMICONDUCTOR DEVICE AND METHOD OF MANUFACTUREWITH SOURCE/DRAIN REGIONS HAVING OPPOSITE CONDUCTIVITIES,” filed on Jun.30, 2015, which application is incorporated herein by reference.

BACKGROUND

Metal-oxide-semiconductor (MOS) devices are key components of integratedcircuits. A MOS device can work in three regions, depending on gatevoltage V_(g) and source-drain voltage V_(ds), linear, saturation, andsub-threshold regions. The sub-threshold region is a region where V_(g)is smaller than the threshold voltage V_(t). A parameter known asSub-threshold Swing (SS) represents the easiness of switching thetransistor current off and thus is an important factor in determiningthe speed of a MOS device. The sub-threshold swing can be expressed as afunction of m*kT/q, where m is a parameter related to capacitance. Thesub-threshold swing of a typical MOS device has a limit of about 60mV/decade (kT/q) at room temperature, which in turn sets a limit forfurther scaling of operation voltage VDD and threshold voltage V_(t).This limitation is due to the diffusion transport mechanism of carriers.For this reason, existing MOS devices typically cannot switch fasterthan 60 mV/decade at room temperatures. The 60 mV/decade sub-thresholdswing limit also applies to FinFETs or ultra thin-body MOSFETs onsilicon-on-insulator (SOI) devices. However, even with better gatecontrol over the channel, an ultra thin body MOSFET on SOI or a FinFETcan only achieve close to, but not below, the limit of 60 mV/decade.With such a limit, faster switching at low operation voltages for futurenanometer devices cannot be achieved.

To solve the above-discussed problem, Tunnel Field Effect Transistors(TFETs) have been explored. TFETs can improve both of these parametersby changing the carrier injection mechanism. In a MOSFET, the SS islimited by the diffusion of carriers over the source-to-channel barrierwhere the injection current is proportional to kT/q. Hence at roomtemperature, the SS is 60 mV/dec. In a TFET, injection is governed bythe band-to-band tunneling from the valence band of the source to theconduction band of the channel. Accordingly, much lower sub-thresholdswing can be achieved. Since the TFETs are often designed to have ap-i-n diode configuration, much lower leakage currents are achieved.Also, the TFETs are more resistant to short-channel effects commonlyseen on MOSFETs.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A-1B illustrate a fin formed from a substrate in accordance withsome embodiments.

FIGS. 2A-2B illustrate a first implantation process in accordance withsome embodiments.

FIGS. 3A-3B illustrate a removal of a first section of the fin inaccordance with some embodiments.

FIGS. 4A-4B illustrate a second implantation process in accordance withsome embodiments.

FIGS. 5A-5B illustrate a third implantation process in accordance withsome embodiments.

FIGS. 6A-6B illustrate a removal of a third section of the fin and afourth implantation process in accordance with some embodiments.

FIG. 7 illustrates formation of spacers in accordance with someembodiments.

FIG. 8 illustrates formation of a first interlayer dielectric inaccordance with some embodiments.

FIGS. 9A-9B illustrate a removal of dummy gate material in accordancewith some embodiments.

FIGS. 10A-10B illustrate a fifth implantation process and a sixthimplantation process in accordance with some embodiments.

FIGS. 11A-11B illustrate a formation of a gate dielectric and gateelectrode in accordance with some embodiments.

FIGS. 12A-12B illustrate a planarization process in accordance with someembodiments.

FIG. 13 illustrates a tunnel field effect transistor in accordance withsome embodiments.

FIGS. 14A-14B illustrate a formation of contacts to the gate electrodein accordance with some embodiments.

FIGS. 15A-15B illustrate an implantation free middle section of the finin accordance with some embodiments.

FIGS. 16A-16B illustrate a first material and a second material in thefin in accordance with some embodiments.

FIGS. 17A-17B illustrate a removal of the first section in accordancewith some embodiments.

FIGS. 18A-18B illustrate a removal of the second section in accordancewith some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

With reference now to FIGS. 1A-1B, wherein FIG. 1B is a cross-sectionalview of FIG. 1A through line 1B-1B′, there is illustrated asemiconductor substrate 101 formed into a fin 103. In an embodiment thesemiconductor substrate 101 may comprise, for example, a III-V material(such as gallium arsenide, indium arsenide, or the like), bulk silicon,doped or undoped, germanium, or an active layer of asemiconductor-on-insulator (SOI) substrate. Generally, an SOI substratecomprises a layer of a semiconductor material, such as silicon, formedon an insulator layer. The insulator layer may be, for example, a buriedoxide (BOX) layer or a silicon oxide layer. The insulator layer isprovided on a substrate, typically a silicon or glass substrate. Othersubstrates, such as a multi-layered or gradient substrate may also beused.

The fin 103 may be formed from the semiconductor substrate 101. In anembodiment the fin 103 may be formed from the semiconductor substrate101 by initially forming a patterned mask 105 over the semiconductorsubstrate 101. The patterned mask 105 may comprise a hard mask of one ormore dielectric layers. For example, the hard mask may be a layer of asilicon dioxide or a silicon nitride formed by, for example, thermaloxidation, chemical vapor deposition (CVD), or the like. Alternatively,the hard mask may be formed of other dielectric materials, such assilicon oxynitride. A multi-layer hard mask, such as layers of silicondioxide and silicon nitride, may also be used. Furthermore, othermaterials, such as a metal, a metal nitride, a metal oxide, or the likemay be used. For example, the hard mask may be formed of tungsten.

The patterned mask 105 is subsequently patterned using, for example,photolithography techniques. Generally, photolithography techniquesinvolve depositing a photoresist material and irradiating thephotoresist material in accordance with a pattern. Thereafter, thephotoresist material is developed to remove a portion of the photoresistmaterial. The remaining photoresist material protects the underlyingmaterial during subsequent processing steps, such as etching. In thiscase, the photoresist material is utilized to create the patterned mask105 to define the fin 103. As such, the patterned mask 105 may be formedto have a first width W₁ of between about 5 nm and about 100 nm, such asabout 10 nm.

Once the patterned mask 105 has been formed, the fin 103 may be formedusing a subtractive etching process along with the patterned mask 105.For example, exposed portions of the semiconductor substrate 101 may beetched to form the fin 103 from the semiconductor substrate 101. In anembodiment the semiconductor substrate 101 may be etched by, forexample, HBr/O₂, HBr/Cl₂/O₂, or SF₆/C₁₂ plasma. In an embodiment the fin103 may be patterned such that it will eventually be used for a channelin a semiconductor device such as a tunneling field effect transistor(TFET).

However, as one of ordinary skill in the art will recognize, thesubtractive process described above to form the fin 103 is intended tobe illustrative and is not intended to limit the embodiments. Rather,any suitable process, such as an epitaxial growth process using thesemiconductor substrate 101 and a mask, may alternatively be utilized toform the fin 103. Any suitable process for forming the fin 103 from thesemiconductor substrate 101 may alternatively be utilized, and all suchprocesses are fully intended to be included within the scope of theembodiments.

FIGS. 1A-1B also illustrate a formation of isolation regions 107 onopposing sides of the fin 103. In an embodiment, the isolation regions107 may be a dielectric material such as an oxide material, ahigh-density plasma (HDP) oxide, or the like. The dielectric materialmay be formed using either a chemical vapor deposition (CVD) method(e.g., the HARP process), a high density plasma CVD method, or othersuitable method of formation as is known in the art.

The region around the fin 103 may be filled by overfilling the regionsaround the fin 103 with the dielectric material and then removing theexcess material from over the fin 103 through a suitable process such aschemical mechanical polishing (CMP), an etch, a combination of these, orthe like. Once the regions around the fin 103 have been filled with thedielectric material, the dielectric material may then be recessed awayfrom the top surface of the fin 103. The recessing may be performed toexpose at least a portion of the sidewalls of the fin 103. Thedielectric material may be recessed using a wet etch by dipping the topsurface of the fin 103 and the dielectric material into an etchant suchas HF, although other etchants, such as H₂, and other methods, such as areactive ion etch, a dry etch with etchants such as NH₃/NF₃, chemicaloxide removal, or dry chemical clean may alternatively be used. Thedielectric material may be recessed to a first depth D₁ from a topsurface of the fin 103 of between about 5 nm and about 300 nm, such asabout 40 nm.

As one of ordinary skill in the art will recognize, however, the stepsdescribed above may be only part of the overall process flow used tofill and recess the dielectric material to form the isolation regions107. For example, lining steps, cleaning steps, annealing steps, gapfilling steps, combinations of these, and the like may also be utilizedto form the isolation regions 107. All of the potential process stepsare fully intended to be included within the scope of the presentembodiment.

Once the isolation regions 107 have been formed, a first dummy gatematerial 109 may be formed over the fin 103. The first dummy gatematerial 109 may comprise a material, such as a doped or undopedpoly-crystalline silicon (or amorphous silicon), a metal (e.g.,tantalum, titanium, molybdenum, tungsten, platinum, aluminum, hafnium,ruthenium), a metal silicide (e.g., titanium silicide, cobalt silicide,nickel silicide, tantalum silicide), a metal nitride (e.g., titaniumnitride, tantalum nitride), other conductive materials, combinationsthereof, or the like. In an embodiment in which the first dummy gatematerial 109 is polysilicon, the first dummy gate material 109 may beformed by depositing doped or undoped polysilicon by low-pressurechemical vapor deposition (LPCVD) to a thickness in the range of about400 Å to about 2,400 Å, such as about 1,400 Å.

Once the first dummy gate material 109 has been formed, the first dummygate material 109 may be patterned into a shape that will eventually beutilized to define a gate electrode 1103 (not illustrated in FIGS. 1A-1Bbut illustrated and discussed below with respect to FIG. 11). In anembodiment the first dummy gate material 109 may be patterned to have afirst length L₁ of between about 5 nm and about 1 μm, such as about 150nm. The first dummy gate material 109 may be patterned using, e.g., aphotolithographic process whereby a photoresist is applied, irradiated,and developed to form a mask, and the mask is then utilized to removeexposed portions of the first dummy gate material 109.

With the first dummy gate material 109 formed over the fin, the fin 103may comprise five distinct sections (located in FIG. 1A beneath thepatterned mask 105 but illustrated using dashed lines for convenience).The first section is a middle section 110 of the fin 103 that is locatedbeneath the first dummy gate material 109. On one side of the middlesection 110, the fin 103 may comprise at its corners regions a firstsection 102 and a second section 104 adjacent to the first section 102.On an opposing side of the middle section 110 the fin 103 may compriseat its corner regions a third section 106, which shares a side of thefin 103 with the middle section 110 and the second section 104, and afourth section 108, which shares an opposite side of the fin 103 withthe middle section 110 and the first section 102.

FIGS. 2A-2B (wherein FIG. 2B is cross-section view of FIG. 2A along line2B-2B′) illustrate a formation of a first implantation mask 201 and afirst implantation (represented in FIGS. 2A-2B by the arrows labeled203) into the first section 102 of the fin 103. In an embodiment thefirst implantation mask 201 is placed and patterned in order to cover atleast a portion of the first dummy gate material 109 as well ascompletely cover the third section 106 of the fin 103 and the fourthsection 108 of the fin 103. In an embodiment the first implantation mask201 may be a photoresist that is first applied and then patterned tocover the first dummy gate material 109 as well the third section 106and the fourth section 108 while leaving the first section 102 of thefin 103 and the second section 104 of the fin 103 exposed. Thepatterning may be performed by exposing the photoresist to a patternedenergy source (e.g., light) to induce a chemical reaction in thoseportions of the photoresist exposed to the energy, and then developingthe photoresist to remove the undesired portions of the photoresist toform the first implantation mask 201.

Alternatively, the first implantation mask 201 may be a hard mask madeof a dielectric material such as silicon nitride. In this embodiment thedielectric material may be initially deposited using a depositionprocess such as chemical vapor deposition, physical vapor deposition, orthe like. Once the dielectric material has been deposited, aphotolithographic masking and etching process may be performed, wherebya photoresist is placed over the dielectric material, exposed to thepatterned energy source, and developed. The patterned photoresist isthen used as a mask along with an etching process (such as a reactiveion etch) to transfer the pattern of the photoresist to the dielectricmaterial.

Once the first implantation mask 201 has been formed to cover a portionof the first dummy gate material 109 as well the third section 106 andthe fourth section 108, the first implantation is performed in order toimplant first dopants into the first section 102 of the fin 103. In anembodiment the first dopants are amorphizing species that will work toamorphize the first section 102 of the fin 103, and may be, e.g., argon,krypton, xenon, indium, arsenic, germanium, combinations of these, orthe like.

In an embodiment the first dopants may be implanted into the firstsection 102 using a process such as a first implantation process,whereby ions of the desired first dopants are accelerated and directedtowards the first section 102 of the fin 103. The ion implantationprocess may utilize an accelerator system to accelerate ions of thedesired first dopant. As such, while the precise energy utilized willdepend at least in part on the fin height and the species used, in oneembodiment the accelerator system may use an energy of from about 0.5KeV to about 30 KeV, such as about 2 KeV. Additionally, in order toimplant the first dopants into the first section 102 within the fin 103and not to implant the first dopants throughout the first section 102and the second section 104, the first dopants are implanted at, e.g., afirst angle α₁ of between about 1° and about 90°, such as about 45°,from perpendicular to the semiconductor substrate 101.

By implanting the first dopants into the first section 102 of the fin103, the first section 102 of the fin 103 with the first dopants mayhave a second width W₂ within the fin 103 of between about 2 nm andabout 50 nm, such as about 5 nm. Additionally, the first dopants may beimplanted to a concentration of between about 1e13 cm⁻³ to about 1e19cm⁻³, such as about 1e15 cm⁻³. However any suitable dimensions andconcentration may alternatively be utilized.

FIGS. 3A-3B (with FIG. 3B being a cross-sectional view of FIG. 3A alongline 3A-3A′) illustrate a removal of the first section 102 from the fin103. In an embodiment the first section 102 may be removed using, e.g.,a wet etch process that utilizes an etchant that selectively removes thematerial of the first section 102 (e.g., the material of the fin 103that has been amorphized by the first dopants) without significantlyremoving the material of the fin 103 outside of the first section 102(e.g., the second section 104). As such, while the precise etchantutilized is dependent at least in part upon the materials used for thefin 103 and the first dopants, in an embodiment in which the fin 103comprises silicon and the first dopants are germanium, an etchant suchas HF may be used to remove the first section 102. However, any suitableetchant or method may alternatively be utilized.

FIGS. 4A-4B illustrate that, once the first section 102 has beenremoved, the second section 104 may be formed into part of a firstsource/drain region 1001 (not fully formed or illustrated in FIGS.4A-4B, but illustrated as fully formed below with respect to FIGS.10A-10B). In an embodiment the second section 104 may be implanted withthe second dopants using a second implantation process (represented inFIG. 4B by the arrows labeled 403) that works to implant second dopants,such as either n-type dopants such as phosphorous, arsenic, or antimonyor p-type dopants such as boron, gallium, or indium, depending on thedesired device to be formed. The second implantation process 403 mayutilize an accelerator system to accelerate ions of the desired seconddopant with an energy of from about 0.5 KeV to about 30 KeV, such asabout 2 KeV. Additionally, because the second section 104 may be fullydoped, the second dopants may be implanted at any desired angle, such asperpendicular to the semiconductor substrate 101. The second dopants maybe implanted to a concentration of between about 1e13 cm⁻³ to about 1e21cm⁻³, such as about 1e19 cm³, although any suitable concentration mayalternatively be utilized.

FIGS. 5A-5B (with FIG. 5B being a cross-sectional view of FIG. 5A alongline 5A-5A′) illustrate a removal of the first implantation mask 201 anda placement of a second implantation mask 501 over at least a portion ofthe first dummy gate material 109 and the second section 104 of the fin103. In an embodiment in which the first implantation mask 201 is aphotoresist, the first implantation mask 201 may be removed using, e.g.,an ashing process, whereby the temperature of the first implantationmask 201 is increased to a point where the first implantation mask 201will undergo a thermal decomposition and is then easily removed.However, any other suitable removal process, such as a wet etch, mayalternatively be used to strip the first implantation mask 201.

Once the first implantation mask 201 has been removed, the secondimplantation mask 501 may be placed over the portion of the first dummygate material 109 and completely covering the second section 104 of thefin 103 while leaving the third section 106 of the fin 103 and thefourth section 108 of the fin 103 exposed by the second implantationmask 501 for further processing. In an embodiment the secondimplantation mask 501 may be similar to the first implantation mask 201,such as by being a photoresist or a hardmask that has been patterned tocover the portion of the first dummy gate material 109 and the secondsection 104 of the fin 103. However, any other suitable material orprocess that may be used to protect the portion of the first dummy gatematerial 109 and the second region 209 of the fin 103 may alternativelybe utilized.

FIGS. 5A-5B also illustrate that, once the second implantation mask 501has been placed, a third implantation process (represented in FIG. 5B bythe arrows labeled 503) may be performed in order to implant thirddopants into the third section 106 of the fin 103. In an embodiment thesecond implantation region 505 is performed in order to implant thirddopants which may be amorphizing species that will work to amorphize thefin 103 within the third section 106, and may be, e.g., argon, krypton,xenon, indium, arsenic, germanium, combinations of these, or the like.

In an embodiment the third dopants may be implanted into the thirdsection 106 using a process such as the third implantation process 503,whereby ions of the desired third dopants are accelerated and directedtowards the third section 106. The third implantation process 503 mayutilize an accelerator system to accelerate ions of the desired thirddopants with energy of from about 0.5 KeV to about 30 KeV, such as about2 KeV. Additionally, in order to implant the third section 106 withinthe fin 103 and not to implant the third dopants throughout the fourthsection 108 of the fin 103, the third dopants are implanted at, e.g., asecond angle α₂ of between about 1° and about 90°, such as about 45°,from perpendicular to the semiconductor substrate 101.

By implanting the third dopants, the third section 106 may be implantedwith a third width W₃ within the fin 103 of between about 2 nm and about50 nm, such as about 5 nm. Additionally, the third dopants may beimplanted within the third section 106 to a concentration of betweenabout 1e13 cm⁻³ to about 1e21 cm⁻³, such as about 1e19 cm⁻³. However,any suitable dimensions and any suitable concentration may alternativelybe utilized.

FIGS. 6A-6B (wherein FIG. 6B illustrates a cross-sectional view of FIG.6A along line 6A-6A′) illustrate a removal of the third section 106 fromthe fin 103. In an embodiment the third section 106 may be removed usinga process similar to the process used to remove the first section 102from the fin 103 (described above with respect to FIGS. 3A-3B). Forexample, a wet etch process that utilizes an etchant that selectivelyremoves the material of the third section 106 (e.g., the material of thefin 103 that has been amorphized by the third dopants) withinsignificantly removing the material of the fin 103 outside of the thirdsection 106 (e.g., the fourth section 108 of the fin 103). As such,while the precise etchant utilized is dependent at least in part uponthe materials used for the fin 103 and the third dopants, in anembodiment in which the fin 103 comprises silicon and the third dopantscomprise germanium, an etchant such as HF may be used to remove thethird section 106. However, any suitable etchant or method mayalternatively be utilized.

FIGS. 6A-6B additionally illustrate that once the third section 108 hasbeen removed, the fourth section 108 of the fin 103 may be formed intopart of a second source/drain region 1003 (not fully illustrated inFIGS. 6A-6B, but fully illustrated and described below with respect toFIG. 10). In an embodiment the fourth section 108 may be implanted usinga fourth implantation process (represented in FIG. 6B by the arrowslabeled 603) that works to implant fourth dopants, such as either n-typedopants such as phosphorous, arsenic, or antimony or p-type dopants suchas boron, gallium, or indium that are of an opposite conductivity typethan the second dopants (implanted within the second section 104). Thefourth implantation process 603 may utilize an accelerator system toaccelerate ions of the desired fourth dopant with energy of from about0.5 KeV to about 30 KeV, such as about 2 KeV. Additionally, because thefourth section 108 of the fin 103 may be fully doped, the fourth dopantsmay be implanted at any desired angle, such as perpendicular to thesemiconductor substrate 101. The fourth dopants may be implanted to aconcentration of between about 1e13 cm⁻³ to about 1e21 cm⁻³, such asabout 1e19 cm⁻³, although any suitable concentration may alternativelybe utilized.

FIG. 7 illustrates a removal of the second implantation mask 501 and aformation of spacers 701 on opposite sides of the first dummy gatematerial 109. In an embodiment in which the second implantation mask 501is a photoresist, the second implantation mask 501 may be removed using,e.g., an ashing process, whereby the temperature of the secondimplantation mask 501 is increased to a point where the secondimplantation mask 501 will undergo a thermal decomposition and is theneasily removed. However, any other suitable removal process, such as awet etch, may alternatively be used to strip the second implantationmask 501.

Once the second implantation mask 501 has been removed, the spacers 701may be formed. In an embodiment the spacers 701 are formed by blanketdepositing a spacer layer (not shown) on the previously formedstructure. The spacer layer may comprise SiN, oxynitride, SiC, SiON,oxide, and the like and may be formed by methods utilized to form such alayer, such as chemical vapor deposition (CVD), plasma enhanced CVD,sputter, and other methods known in the art. The spacers 701 may then bepatterned, such as by one or more etches to remove the spacer layer fromthe horizontal surfaces of the structure and from along two edges of thefirst dummy gate material 109.

FIG. 8 illustrates a formation of a first ILD 801 over the semiconductorsubstrate 101 and over the first dummy gate material 109 and the spacers701. In an embodiment the first ILD 801 may be formed by ALD, PVD, CVD,or other acceptable methods for forming an ILD. The first ILD 801 maycomprise doped or undoped silicon oxide, although other materials suchas silicon nitride doped silicate glass, high-k materials, combinationsof these, or the like, may alternatively be utilized. After formation ofthe first ILD 801, the first ILD 801, the first dummy gate material 109and the spacers 701 may be planarized using suitable techniques such asa chemical mechanical polish (CMP) process. The planarization processwill re-expose the first dummy gate material 109 as well as the spacers701 for further processing, while protecting the other underlyingstructures.

FIGS. 9A-9B (wherein FIG. 9B being a cross-sectional view of FIG. 9Aalong line 9B-9B′) illustrate that, once the first ILD 801, the firstdummy gate material 109 and the spacers 701 have been planarized, thefirst dummy gate material 109 may be removed. In an embodiment the firstdummy gate material 109 is removed using a removal process suitable forthe material that was chosen to form the first dummy gate material 109.As such, while the precise method of removal will be at least in partdependent upon the material chosen, in an embodiment in which the firstdummy gate material 109 is polysilicon, the first dummy gate material109 may be removed using a process such as plasma etching with anetchant such as HBr/Cl₂, F₂, or a wet etching such as NH₄OH,combinations of these, or the like.

FIGS. 10A-10B (wherein FIG. 10B is a cross-sectional view of FIG. 1Aalong line 10A-10A′) illustrate a formation of a first implantationregion 1002 and a second implantation region 1004 within the middlesection 110 the fin 103 that had been previously covered by the firstdummy gate material 109. In an embodiment the first implantation region1002 may be implanted with fifth dopants that are similar to the seconddopants that were previously implanted into the second section 104 (seeFIGS. 4A-4B for the second implantation process 403). Together, thefirst implantation region 1002 (within the middle section 110 of the fin103) and the second section 104 (which also be seen as a first extensionregion extending away from the first implantation region 1002) form thefirst source/drain region 1001 (seen in FIG. 10A by the dashed lines) ofthe TFET.

In an embodiment the fifth dopants may be implanted into the firstimplantation region 1002 using a process such as a fifth implantationprocess (represented in FIG. 10B by the arrows labeled 1005), wherebyions of the desired fifth dopants are accelerated and directed towardsthe middle section 110 of the fin 103 to form the first implantationregion 1002. The fifth implantation process 1005 may utilize anaccelerator system to accelerate ions of the desired fifth dopant withan energy of from about 0.5 KeV to about 30 KeV, such as about 2 KeV.Additionally, in order to form the first implantation region 1002 withinthe middle section 110 of the fin 103 and not to implant the fifthdopants throughout the middle section 110 of the fin 103, the fifthdopants are implanted at, e.g., a third angle α₃ of between about 1° andabout 90°, such as about 45°, from perpendicular to the semiconductorsubstrate 101.

Using the fifth implantation process 1005, the first implantation region1002 may be formed with a fourth width W₄ within the fin 103 of betweenabout 2 nm and about 50 nm, such as about 5 nm. Additionally, the fifthdopants may be implanted to a concentration of between about 1e13 cm⁻³to about 1e17 cm⁻³, such as about 1e16 cm⁻³. However, any desireddimensions and concentrations may alternatively be utilized.

The second implantation region 1004 may be formed by implanting themiddle section 110 of the fin 103 with sixth dopants that are similar tothe fourth dopants that were previously implanted into the fourthsection 108 of the fin 103 (see FIGS. 6A-6B). Together, the secondimplantation region 1004 (within the middle section 110 of the fin 103)and the fourth section 108 (which may be seen as a second extensionregion extending away from the second implantation region 1004) form thesecond source/drain region 1003 (seen in FIG. 10A by the dashed lines)of the TFET. The second implantation region 1004 may be formed using asixth implantation process (represented in FIG. 10B by the arrowslabeled 1007). In an embodiment the sixth implantation process 1007 maybe ion implantation process, whereby ions of the desired sixth dopantsare accelerated and directed towards the middle section 110 of the fin103. The sixth implantation process 1007 may utilize an acceleratorsystem to accelerate ions of the desired sixth dopant with an energy offrom about 0.5 KeV to about 30 KeV, such as about 2 KeV. Additionally,in order to form the second implantation region 1004 within the fin 103and not to implant the sixth dopants throughout the middle section ofthe fin 103 (e.g., within the first implantation region 1002), the sixthdopants are implanted at, e.g., a fourth angle α₄ of between about 1°and about 90°, such as about 45° from perpendicular to the semiconductorsubstrate 101.

By using the sixth implantation process 1007, the second implantationregion 1004 may be formed with a fifth width W₅ within the fin 103 ofbetween about 2 nm and about 50 nm, such as about 5 nm. Additionally,the sixth dopants may be implanted to a concentration of between about1e13 cm⁻³ to about 1e17 cm⁻³, such as about 1e16 cm⁻³. However, anysuitable dimensions and any suitable concentrations may alternatively beutilized.

However, while precise examples are of the doping concentrations areprovided above, these examples are only intended to be illustrative andare not intended to be limiting. Rather, the precise doping levelsutilized may involve a trade-off between good electrostatic control fromthe gate (wherein a lower doping level may be desired, although as a finis reduced in size a higher doping may be utilized) and higher tunnelingefficiency (wherein a higher doping level may be desired).

For example, in a particular embodiment the second implantation region1004 may be implanted to have a high doping concentration on the sourceconnected side, such as having a doping concentration greater than10¹⁹/cm³ and have a lower doping concentration on the drain connectedside, such as having a doping concentration less than about 10¹⁷/cm³. Bymodifying the doping concentrations on either side, the performance ofthe TFET formed from the fin 103 may be tuned.

FIGS. 11A-11B (wherein FIG. 11B is a cross-sectional view of FIG. 11Athrough line 11A-11A′) illustrate a formation of a gate dielectric 1101and a gate electrode 1103 over the fin 103. The gate dielectric 1101(not visible in FIG. 4A but seen in FIG. 4B) may be formed by thermaloxidation, chemical vapor deposition, sputtering, or any other methodsknown and used in the art for forming a gate dielectric. The gatedielectric 1101 may comprise a material such as silicon dioxide orsilicon oxynitride with a thickness ranging from about 3 angstroms toabout 100 angstroms, such as about 10 angstroms. The gate dielectric1101 may alternatively be formed from a high permittivity (high-k)material (e.g., with a relative permittivity greater than about 5) suchas lanthanum oxide (La₂O₃), aluminum oxide (Al₂O₃), hafnium oxide(HfO₂), hafnium oxynitride (HfON), or zirconium oxide (ZrO₂), orcombinations thereof, with an equivalent oxide thickness of about 0.5angstroms to about 100 angstroms, such as about 10 angstroms or less.Additionally, any combination of silicon dioxide, silicon oxynitride,and/or high-k materials may also be used for the gate dielectric 1101.

The gate electrode 1103 may comprise a conductive material and may beselected from a group comprising of polycrystalline-silicon (poly-Si),poly-crystalline silicon-germanium (poly-SiGe), metallic nitrides,metallic silicides, metallic oxides, metals, combinations of these, andthe like. Examples of metallic nitrides include tungsten nitride,molybdenum nitride, titanium nitride, and tantalum nitride, or theircombinations. Examples of metallic silicide include tungsten silicide,titanium silicide, cobalt silicide, nickel silicide, platinum silicide,erbium silicide, or their combinations. Examples of metallic oxidesinclude ruthenium oxide, indium tin oxide, or their combinations.Examples of metal include tungsten, titanium, aluminum, copper,molybdenum, nickel, platinum, etc.

The gate electrode 1103 may be deposited by chemical vapor deposition(CVD), sputter deposition, or other techniques known and used in the artfor depositing conductive materials. The thickness of the gate electrode1103 may be in the range of about 200 angstroms to about 4,000angstroms. Ions, if desired, may or may not be introduced into the gateelectrode 1103 at this point.

FIGS. 12A-12B (wherein FIG. 12B is a cross-sectional view of FIG. 12Athrough line 12A-12A′) illustrate a deposition of a second ILD 1201 overthe gate electrode 1103. In an embodiment the second ILD 1201 may beformed by ALD, PVD, CVD, or other acceptable methods for forming an ILD.The second ILD 1201 may comprise doped or undoped silicon oxide,although other materials such as silicon nitride doped silicate glass,high-k materials, combinations of these, or the like, may alternativelybe utilized. The second ILD 1201 may be deposited in order to cover thegate electrode 1103.

FIGS. 12A-12B also illustrate that, once the second ILD 1201 has beendeposited, a planarization process is performed in order to removeexcess material from the second ILD 1201, the gate electrode 1103, andthe gate dielectric 1101. In an embodiment the planarization process maybe a chemical mechanical polishing (CMP) process, in which chemicals andabrasives are utilized to react and grind the material of the second ILD1201, the gate electrode 1103, and the gate dielectric 1101 from overthe fin 103 (while leaving at least a portion of the patterned mask 105)and planarize the gate electrode 1103 with the spacers 701 and thesecond ILD 1201. However, any suitable planarization process mayalternatively be utilized.

FIG. 13 illustrates a three-dimensional view of the first source/drainregion 1001, the second source/drain region 1003, the gate dielectric1101, and the gate electrode 1103, with the semiconductor substrate 101,the isolation regions 107, the first ILD 801, the spacers 701, and thesecond ILD 1201 removed for convenience. As can be seen, in thisembodiment the tunneling of the TFET will occur laterally in a directionperpendicular parallel with the semiconductor substrate 101 (asrepresented in FIG. 13 by the arrow labeled 1301). As such, the overlapsize of the TFET (the overlap between the first source/drain region 1001and the second source/drain region 1003) may be increased by simplyincreasing the height of the fin 103 and with no subsequent increase inthe overall cell area.

Additionally, by using the processes described herein, the TFET may beformed using finFET processes and, as such, may be incorporated intocompatible finFET processes. Also, these processes disclosed herein areself-aligning processes, and use both the first dummy gate material 109along with the first implantation mask 021 and the second implantationmask 501 so that the precision that is desired from the photoresist maybe reduced.

FIGS. 14A-14B (wherein FIG. 14B is a cross-sectional view of FIG. 14Athrough line 14B-14B′) illustrate a formation of a first contact 1401 inelectrical connection with a first section 1103A of the gate electrode1103 and a second contact 1403 in electrical connection with a secondsection 1103B of the gate electrode 1103. In an embodiment the firstcontact 1401 and the second contact 1403 may be formed by initiallyforming contact openings (not separately illustrated) through the secondILD 1201 in order to expose the first section 1103A of the gateelectrode 1103 and the second section 1103B of the gate electrode 1103.The contact openings may be formed, for example, using aphotolithographic masking and etching process.

Once the contact openings have been formed, the contact openings may befilled with a barrier layer and a conductive material (not separatelylabeled in FIGS. 14A-14B). In an embodiment, the barrier layer may beformed of one or more layers of titanium, titanium nitride, tantalum,tantalum nitride, tungsten nitride, ruthenium, rhodium, platinum, othernoble metals, other refractory metals, their nitrides, combinations ofthese, or the like. The barrier layer may be formed through chemicalvapor deposition, although other techniques such as PVD or ALD couldalternatively be used. The barrier layer may be formed to a thickness ofabout 5 Å to about 500 Å.

After the barrier layer has been formed, the conductive material may beformed to fill the contact openings. The conductive material may beformed be initially forming a seed layer (also not individually shown inFIGS. 14A-14B) over the barrier layer. The seed layer may be depositedby PVD, ALD or CVD, and may be formed of tungsten, copper, or copperalloys, although other suitable methods and materials may alternativelybe used if desired. Additionally, while the thickness of the seed layerwill be dependent at least in part on the depth of the contact openings,the seed layer may have a thickness of between about 5 Å and about 1,000Å.

Once the seed layer has been formed, the conductive material may beformed onto the seed layer. The conductive material may comprisetungsten, although other suitable materials such as aluminum, copper,tungsten nitride, ruthenium, silver, gold, rhodium, molybdenum, nickel,cobalt, cadmium, zinc, alloys of these, combinations thereof, and thelike, may alternatively be utilized. The conductive material may beformed by electroplating the conductive material onto the seed layer,filling and overfilling the contact openings.

Once the contact openings have been filled, excess barrier layer, seedlayer, and conductive material outside of the contact openings may beremoved through a planarization process such as chemical mechanicalpolishing (CMP), although any suitable removal process may be used. Theplanarization process will also planarize the first contact 1401 and thesecond contact 1403 with the second ILD 1201, the first section 1103A ofthe gate electrode 1103, the second section 1103B of the gate electrode1103, and the gate dielectric 1101.

FIGS. 15A-15B (wherein FIG. 15B is a cross-sectional view of FIG. 15Athrough line 15B-15B′) illustrate another embodiment in which the fifthimplantation process 1005 and the sixth implantation process 1007 arenot performed, thereby leaving the middle section 110 of the fin 103with only those dopants, if any, that were present when the fin wasinitially formed. In this embodiment, the first source/drain region 1001comprises only the second section 104 of the fin 103 (that had beendoped using the second implantation process 403 (see FIGS. 4A-4B)) andthe second source/drain region 1003 comprises only the fourth section108 of the fin 103 (that had been doped using the fourth implantationprocess 603 (see FIGS. 6A-6B)).

In this embodiment, the TFET will still operate if two different gatevoltages are applied to the first section 1103A of the gate electrode1103 and to the second section 1103B of the gate electrode 1103. Forexample, if a first voltage (to create an electrostatic doping) ofbetween about −15V and about +15V, such as about +/−1V is applied to thefirst section 1103A of the gate electrode 1103 and a second voltage (tobias the transistor) of between about −1V and about +1V, such as about+/−0.5V, is applied to the second section 1103A of the gate electrode1103, the TFET may be switched even without the doping immediatelyadjacent to the gate electrode 1103.

FIGS. 16A-16B (wherein FIG. 16B is a cross-sectional view of FIG. 16Aalong line 16B-16B′) illustrates another embodiment in which the fin 103is formed from a first material 1601 and a second material 1603 with adifferent etch resistivity than the first material 1601. In anembodiment the first material 1601 may comprise, e.g., a III-V materialthat has already been doped with n-type dopants, while the secondmaterial 1603 may be, e.g., a III-V material that has already been dopedwith p-type dopants.

In an embodiment the first material 1601 may be formed by initiallyplacing and patterning a photoresist in order to expose only theportions of the semiconductor substrate 101 that will become the firstmaterial 1601 and then using a seventh implantation process (notseparately illustrated) in order to implant the n-type dopants into thesemiconductor substrate 101 to form the first material 1601. Once thefirst material 1601 has been formed, the second material 1603 may beformed by placing and patterning another photoresist in order to coverthe first material 1601 and expose the portions of the semiconductorsubstrate 101 that will become the second material 1603 and then usingan eight implantation process (also not separately illustrated) in orderto implant the p-type dopants into the semiconductor substrate 101. Oncethe first material 1601 and the second material 1603 have been formed,the fin 103 may be patterned such that the first material 1601 makes upthe second section 104 and the third section 106 of the fin 103 and thesecond material 1603 makes up the first section 102 and the fourthsection 108 of the fin 103.

However, the above described process for forming the first material 1601and the second material 1603 is intended to be illustrative and is notintended to limiting. Rather, any suitable process for forming the firstmaterial 1601 and the second material 1603, such as performing a seriesof epitaxial growths that grows the first material 1601 separately fromthe second material 1603, may alternatively be used. All such processesare fully intended to be included within the scope of the embodiments.

FIGS. 17A-17B (wherein FIG. 17B is a cross-sectional view of FIG. 17Athrough line 17B-17B′) illustrates a removal of the first section 102 ofthe fin 103. In an embodiment, because the second material 1603 has adifferent etch selectivity than the first material 1601, the removal offirst section 102 may be performed without the first implantationprocess 203. As such, the removal of the first section 102 may beperformed by placing the first implantation mask 201 and thenselectively removing the first section 102 without significantlyremoving the second section 104 using, e.g., a wet etch process. In anembodiment in which the first material 1601 is SiGe and the secondmaterial 1603 is Ge, the etchant used may be HCl.

FIGS. 18A-18B (wherein FIG. 18B is a cross-sectional view of FIG. 18Athrough line 18B-18B′) illustrate a removal of the third section 106 ofthe fin 103. In an embodiment, because the first material 1601 has adifferent etch selectivity than second material 1603, the removal of thethird section 106 may be performed without the third implantationprocess 503. As such, the removal of the third section 106 may beperformed by placing the second implantation mask 501 and thenselectively removing the third section 106 without significantlyremoving the fourth section 108 using, e.g., a wet etch process. In anembodiment in which the first material 1601 is SiGe and the secondmaterial 1603 is Ge, the etchant used may be a mixture of ammoniahydroxide, hydrogen peroxide, and water (e.g., in a 0.25:1:5 ratio),such as an APM clean mixture.

By using the first material 1601 and the second material 1603, theremainder of the steps as described above may be used to form the TFETwithout requiring the amorphizing implantations in order to adjust theselectivity of the first section 102 and the third section 106, whilethe remainder of the steps (such as replacing the first dummy gatematerial 109) may be performed as described above. As such, theamorphizing implantation steps may be avoided. Such a reduction in thenumber of process steps helps to make the overall process moreefficient.

One embodiment is a semiconductor device. The semiconductor deviceincludes a semiconductor substrate having a fin which has a middle finsection, a first fin section which extends along a first sidewall of themiddle fin section in a first direction, and a second fin section whichextends along a second sidewall of the middle fin section in a seconddirection opposite the first direction. The first fin section has afirst width and the middle fin section has a second width greater thanthe first width.

Another embodiment is semiconductor device which includes a firstsection, second section, and third section. The first section has afirst width between a first sidewall and a second sidewall. The firstsection has a first conductivity. The second section has a second widthbetween a third sidewall and a fourth sidewall. The third section of thesemiconductor fin has a third width between a fifth sidewall and a sixthsidewall. The third section has a second conductivity opposite to thefirst conductivity. The first section extends from the second sectionand the first sidewall is coplanar with the third sidewall. The thirdsection extends from the second section in an opposite direction fromthe first section, wherein the fifth sidewall is coplanar with thefourth sidewall. The second width is greater than the first width andthe third width.

Another embodiment is semiconductor device which includes asemiconductor middle fin section with a first width over a substrate.First dopants of a first conductivity are included within a firstportion of the semiconductor middle fin section. Second dopants of asecond conductivity opposite the first conductivity are also within asecond portion of the semiconductor middle fin section, wherein thefirst portion and the second portion are in physical contact with eachother. A first extension region in is in physical contact with the firstportion and extends away from the semiconductor middle fin section. Thefirst extension region has a second width less than the first width.Third dopants of the first conductivity are within the first extensionregion. A second extension region is in physical contact with the secondportion and extends in an opposite direction than the first extensionregion. The second extension region has a third width less than thefirst width. Fourth dopants of the second conductivity are within thesecond extension region.

In accordance with an embodiment, a method of manufacturing asemiconductor device comprising forming a fin from a semiconductorsubstrate is provided. A first section is removed from a first cornerregion of the fin and a second section is removed from a second cornerregion of the fin, wherein the second section is on an opposite side ofthe fin from the first section. First dopants are implanted to form afirst source/drain region within the fin, and second dopants areimplanted to form a second source/drain region within the fin inphysical contact with the first source/drain region, wherein the secondsource/drain region has an opposite conductivity than the firstsource/drain region.

In accordance with another embodiment, a method of manufacturing asemiconductor device comprising patterning a fin from a semiconductorsubstrate using a patterned mask is provided. The fin comprises a middlesection, a first portion and a second portion on a first side of themiddle section, and a third portion and a fourth portion on a secondside of the middle section opposite the first side, wherein the firstportion, the middle section, and the fourth portion share a side of thefin. First ions are implanted into the first portion, and the firstportion is removed. Second ions are implanted into the third portion,and the third portion is removed. Third ions and fourth ions areimplanted into the middle section, wherein the third ions have a firstconductivity and the fourth ions have a second conductivity differentfrom the first conductivity. A gate electrode is formed adjacent to themiddle section.

In accordance with yet another embodiment, a semiconductor devicecomprising a semiconductor middle fin section with a first width over asubstrate is provided. First dopants of a first conductivity are withina first portion of the semiconductor middle fin section. Second dopantsof a second conductivity opposite the first conductivity are within asecond portion of the semiconductor middle fin section, wherein thefirst portion and the second portion are in physical contact with eachother. A first extension region is in physical contact with the firstportion and extending away from the semiconductor middle fin section,wherein the first extension region has a second width less than thefirst width. Third dopants of the first conductivity are within thefirst extension region. A second extension region is in physical contactwith the second portion and extending in an opposite direction than thefirst extension region, wherein the second extension region has a thirdwidth less than the first width. Fourth dopants of the secondconductivity are within the second extension region.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A semiconductor device, comprising: asemiconductor substrate having a fin, the fin comprising a middle finsection, a first fin section extending along a first sidewall of themiddle fin section in a first direction, and a second fin sectionextending along a second sidewall of the middle fin section in a seconddirection opposite the first direction, and wherein the first finsection has a first width and the middle fin section has a second widthgreater than the first width.
 2. The semiconductor device of claim 1,further comprising: a first dopant of a first conductivity, wherein thefirst dopant is within the first fin section and the first sidewall ofthe middle fin section; and a second dopant of a second conductivity,wherein the second dopant is within the second fin section and thesecond sidewall of the middle fin section.
 3. The semiconductor deviceof claim 2, wherein the second conductivity is opposite the firstconductivity.
 4. The semiconductor device of claim 1, wherein: a topsurface of the first fin section, a top surface of the second finsection, and a top surface of the middle fin section are all level. 5.The semiconductor device of claim 1, wherein the second width of themiddle fin section is twice the first width of the first fin section. 6.The semiconductor device of claim 1, further comprising: a gatestructure formed over the middle fin section, the gate structure notbeing formed over the first fin section or the second fin section. 7.The semiconductor device of claim 6, wherein the gate structurecomprises: a gate dielectric in contact with the middle fin section; anda gate electrode over the gate dielectric.
 8. A semiconductor device,comprising: a first section of a semiconductor fin having a first widthbetween a first sidewall and a second sidewall, the first section havinga first conductivity; a second section of the semiconductor fin having asecond width between a third sidewall and a fourth sidewall; a thirdsection of the semiconductor fin having a third width between a fifthsidewall and a sixth sidewall, the third section having a secondconductivity opposite to the first conductivity, and wherein the firstsection extends from the second section and the first sidewall iscoplanar with the third sidewall, wherein the third section extends fromthe second section in an opposite direction from the first section,wherein the fifth sidewall is coplanar with the fourth sidewall, andwherein the second width is greater than the first width and the thirdwidth.
 9. The semiconductor device of claim 8, wherein the secondsection comprises a first portion adjacent to the first section and asecond portion adjacent to the third section, wherein the first portionhas the first conductivity, and wherein the second portion has thesecond conductivity.
 10. The semiconductor device of claim 9, whereinthe first conductivity is associated with a first dopant, and the secondconductivity is associated with a second dopant, wherein a concentrationof the first dopant in the first section is greater than a concentrationof the first dopant in the second section.
 11. The semiconductor deviceof claim 10, wherein a concentration of the second dopant in thirdsection is greater than a concentration of the second dopant in thesecond section.
 12. The semiconductor device of claim 8, wherein thesecond sidewall is perpendicular to an adjacent end wall of the secondsection.
 13. The semiconductor device of claim 8, further comprising: agate dielectric over the second section; and a gate electrode over thegate dielectric.
 14. The semiconductor device of claim 8, wherein thesecond section comprises a III-V material.
 15. A semiconductor devicecomprising: a semiconductor middle fin section with a first width over asubstrate; first dopants of a first conductivity within a first portionof the semiconductor middle fin section; second dopants of a secondconductivity opposite the first conductivity within a second portion ofthe semiconductor middle fin section, wherein the first portion and thesecond portion are in physical contact with each other; a firstextension region in physical contact with the first portion andextending away from the semiconductor middle fin section, wherein thefirst extension region has a second width less than the first width;third dopants of the first conductivity within the first extensionregion; a second extension region in physical contact with the secondportion and extending in an opposite direction than the first extensionregion, wherein the second extension region has a third width less thanthe first width; and fourth dopants of the second conductivity withinthe second extension region.
 16. The semiconductor device of claim 15,wherein a concentration of first dopants in the first extension regionis greater than a concentration o f first dopants in the semiconductormiddle fin section.
 17. The semiconductor device of claim 15, furthercomprising: a gate dielectric adjacent to the semiconductor middle finsection; and a gate electrode adjacent to the gate dielectric.
 18. Thesemiconductor device of claim 17, wherein the semiconductor middle finsection extends a first distance away from the substrate, and whereinthe gate electrode extends no further than the semiconductor middle finsection.
 19. The semiconductor device of claim 17, further comprising adielectric material over the substrate, wherein the dielectric material,the gate electrode, and the semiconductor middle fin section are planarwith each other.
 20. The semiconductor device of claim 15, wherein thesemiconductor middle fin section comprises a III-V material.